Habitrail OVO Tube (25 cm/10 in) adds length to hamster setups, enhancing your pets living experience and increasing exercise and stimulation. OVO Tube has air vents to improve airflow and ensure that your hamster's home is always fresh Based on extensive behavioral studies, Habitrail OVO housing and accessories are designed to help enhance your pet hamster's quality of life. Completely redesigned, re-tooled and reinvigorated, OVO brings even more interesting and entertaining venues in which hamsters can explore, burrow, snooze, exercise or simply chill out.